chemistry

Isoflurane

Isoflurane is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Isoflurane rather than just read about it. In short: Isoflurane, sold under the brand name Forane among others, is a halogenated ether used as a general anesthetic. It can be used to start or maintain anesthesia; however, other medications are often used to start anesthesia, due to airway irritation with isoflurane.

Key takeaways

Isoflurane belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Isoflurane to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Isoflurane from memory before moving on to harder problems.

Reference excerpt

Isoflurane, sold under the brand name Forane among others, is a halogenated ether used as a general anesthetic. It can be used to start or maintain anesthesia; however, other medications are often used to start anesthesia, due to airway irritation with isoflurane. Isoflurane is an inhalational anesthetic given via inhalation. Isoflurane was approved for medical use in the United States in 1979. It is on the World Health Organization's List of Essential Medicines.

Medical uses Isoflurane is indicated for induction and maintenance of general anesthesia. Isoflurane is always administered in conjunction with air or pure oxygen. Often, nitrous oxide is also used. Although its physical properties imply that anaesthesia can be induced more rapidly than with halothane, its pungency can irritate the respiratory system, negating any possible advantage conferred by its physical properties. Thus, it is mostly used in general anesthesia as a maintenance agent after induction of general anesthesia with an intravenous agent such as thiopentone or propofol.

Mechanism of action Similar to many general anesthetics, the exact mechanism of the action has not been clearly delineated. Isoflurane reduces pain sensitivity (analgesia) and relaxes muscles. Isoflurane likely binds to GABA, glutamate and glycine receptors, but has different effects on each receptor. Isoflurane acts as a positive allosteric modulator of the GABAA receptor in electrophysiology studies of neurons and recombinant receptors. It potentiates glycine receptor activity, which decreases motor function. It inhibits receptor activity in the NMDA glutamate receptor subtypes. Isoflurane inhibits conduction in activated potassium channels. Isoflurane also affects intracellular molecules. It inhibits plasma membrane calcium ATPases (PMCAs) which affects membrane fluidity by hindering the flow of Ca2+ (calcium ions) out across the membrane, this in turn affects neuron depolarization. It binds to the D subunit of ATP synthase and NADH dehydrogenase. General anaesthesia with isoflurane reduces plasma endocannabinoid AEA concentrations, and this could be a consequence of stress reduction after loss of consciousness.

Adverse effects Side effects of isoflurane include a decreased ability to breathe (respiratory depression), low blood pressure, and an irregular heartbeat. Isoflurane can cause a sudden decrease in blood pressure due to dose-dependent peripheral vasodilation. This may be specially marked in hypovolemic patients. Serious side effects can include malignant hyperthermia or high blood potassium. It should not be used in patients with a history of malignant hyperthermia in either themselves or their family members. It is unknown if its use during pregnancy is safe for the fetus, but use during a cesarean section appears to be safe. Animal studies have raised safety concerns of certain general anesthetics, in particular ketamine and isoflurane, in young children. The risk of neurodegeneration was increased in combination of these agents with nitrous oxide and benzodiazepines such as midazolam. Whether these concerns occur in humans is unclear.

Elderly Biophysical studies using NMR spectroscopy has provided molecular details of how inhaled anesthetics interact with three amino acid residues (G29, A30 and I31) of amyloid beta peptide and induce aggregation. This area is important as "some of the commonly used inhaled anesthetics may cause brain damage that accelerates the onset of Alzheimer's disease".

Anesthetic physical properties Isoflurane has a minimum alveolar concentration (MAC) of 1.15 vol %. The blood/gas partition coefficient is 1.4, and the oil/gas partition coefficient is 98. Its vapor pressure at 20 °C (68 °F) is 31.7 kilopascals (238 mmHg). It is administered as a racemic mixture of (R)- and (S)-optical isomers. It is non-combustible but can give off irritable and toxic fumes when exposed to flame.

History Together with enflurane and halothane, isoflurane began to replace the flammable ethers used in the pioneer days of surgery; this shift began in the 1940s to the 1950s. Its name comes from being a structural isomer of enflurane, hence they have the same empirical formula.

Environment The average lifetime of isoflurane in the atmosphere is 3.2 years, its global warming potential is 510 (times greater than carbon dioxide) and yearly emissions as of 2015 were 880 tons.

Veterinary use Isoflurane is used for the induction and maintenance of general anesthesia in horses and dogs. It is also used on koalas. Isoflurane is also commonly used in lab settings as general anesthesia for work on laboratory mice and rats.

References

External links U.S. patent 3,535,388 - 1-chloro-2,2,2-trifluoroethyl difluoromethyl ether U.S. patent 3,535,425 - 1-chloro-2,2,2-trifluoroethyl difluoromethyl ether as an anesthetic agent

Illustrations

Worked examples

Example 1 — a first encounter with Isoflurane

Start with the simplest possible case. Write down what Isoflurane claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Isoflurane before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Isoflurane ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Isoflurane

In research: Isoflurane appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Isoflurane in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Isoflurane is common in secondary-school and first-year university syllabi. It links to neighbouring topics 5-HT3 receptor positive allosteric modulators, Difluoromethoxy compounds, Ethers, so understanding it makes those chapters shorter.
In everyday life: Look for Isoflurane outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Isoflurane in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Isoflurane means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Isoflurane out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Isoflurane in simple terms?

Why does Isoflurane matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Isoflurane?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Isoflurane.